darkside Posted March 15, 2009 Share Posted March 15, 2009 I hope I can get some clear answers from you guys here, so here's the deal: I've got an old Harman Kardon Citation 12 that, after much trouble shooting, I've found has a bad differential pair on the right channel, causing the amp to click and pop, which brings the possiblity of blowing tweeters, which is why I'm not using it. I went through a long process of figuring out that that is what's wrong and was then told by some nice people on another forum that, since the particular part is a) no longer made and two PNP transistors in a single part, I should replace that one transistor with a matched pair of 2N5087s, which makes plenty of sense. However, do transistors for this particular amp (keep in mind that it's about 40 years old) need to be matched and if so, how do I go about matching them? Thanks! Quote Link to comment Share on other sites More sharing options...
JohnA Posted March 16, 2009 Share Posted March 16, 2009 There are expensive testing devices to match transistors that were rare 20 years ago when I needed one for a Yamaha CA-800 I had. The output transistors were obsolete. I ended up going to the electronics store with a multi-meter and measuring the DCR between all of the pins on several transistors and picked the closest matching ones to use. I also replaced the good ones in the other channel, so they all would march (admitted overkill). Quote Link to comment Share on other sites More sharing options...
darkside Posted March 16, 2009 Author Share Posted March 16, 2009 Thanks for the response. Unfortunately, I can't say I know what DCR is, maybe I'm just slow today or something [:S] Would it be worth it to match them based on each transistors beta, which is what I was told to do elsewhere, or is that the same thing as what you just said? Quote Link to comment Share on other sites More sharing options...
darkside Posted March 18, 2009 Author Share Posted March 18, 2009 Anyone? Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted March 19, 2009 Share Posted March 19, 2009 DCR is usally the DC resistance in ohms. As for matching or not, I cannot help. Quote Link to comment Share on other sites More sharing options...
darkside Posted March 19, 2009 Author Share Posted March 19, 2009 Ok, thanks. Quote Link to comment Share on other sites More sharing options...
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